One-dimensional finite element analysis of the soil plug in open-ended piles under axial load
In the offshore industry, open-ended steel piles are primarily designed using one of three pile design methods: the API (2011), the ICP (2005) and the UWA (2005). The soil plug, inside the pile, is considered differently in each of the methods, producing different pile lengths due to the varying assumptions adopted. A one-dimensional finite element method has been used to analyse the behaviour of the resistive components of the soil-pile-plug system. This adopts the principle of virtual work to solve the coupled differential equations enabling the contribution of each component to be isolated. Using this method, a more realistic axial pile response can be modelled which directly influences the behaviour of the soil plug. Predictions from the method have been compared to the results of double walled pile tests which show the mobilisation of the external shaft friction from the top downwards, and the internal friction from the base upwards.